Transmissions as described above are known from EP-A-0 451 887 in which respective primary and secondary control means are connected to the pressure chambers of each of the adjustable pulley discs. The control means are embodied as feedback loops in which, on the basis of a difference-signal between a desired value and a measured value, the regulator provides a hydraulic pressure regulator with a signal which is used to precipitate the primary and secondary pressure in the pressure chambers of the adjustable pulley discs.
The disadvantage of the known transmission is that a swift response to a swift variation in the desired value of the supplied pressure is only possible for relatively large set trigger values or amplification factors in the regulator concerned, whence the probability of instability-occurrence in the control system shows a significant increase, with corresponding undesired increase in wear and reduction in efficiency of the transmission.